In general, a water pump motor is used to drive a water pump that is installed in a drain water tank of a washing machine, or is used as a driving source of a water pump that is used for circulation of a coolant that cools an engine. The water pump equipped with the water pump motor works under an environment that the inside of the water pump always directly contacts water.
Thus, a component that is called a mechanical seal is used in a water pump for sealing purposes in order to protect a motor from water when the water of the inside of the water pump is drained to the outside of the water pump or in order to prevent failure of bearings or shortened life of belts due to leakage of a coolant.
A conventional water pump that uses a mechanical seal requires a separate additional post-processing work in order to have the mechanical seal. Accordingly, a processing cost and a material cost for the mechanical seal rise up to thereby become a factor of raising the prime cost of the water pump using a water pump motor. In addition, water or foreign matters flowing from the outside of the water pump may be introduced into the water pump motor, to thereby cause breakdown of the motor.
A bearing structure that is used in a water pump motor having a can cover in order to protect the water pump motor was disclosed in the U.S. Pat. No. 4,277,115. The bearing structure that is used in the disclosed water pump motor having the can cover is configured to include a ring of an elastomer or of felt that is disposed between a calotte bearing and a bearing support element, and grooves that are formed in the bearing support element and the calotte bearing near the ring. Here, the ring of the elastomer or of the felt is disposed between the calotte bearing and the bearing support element and the calotte bearing and the bearing support element are provided with grooves formed in the region of the ring. The calotte bearing mount is particularly useful in pumps with canned motors for delivery of electrolyte liquid in fuel cell units.
In the above-described water pump having the can cover, water introduced into the water pump motor from the water pump can be blocked to some extent. However, the can cover should be separately produced to be assembled with the motor, to thereby cause the prime cost of the water pump to rise and productivity to lower. Further, a waterproof structure for water entering from the outside of the water pump motor is not presented, to thus require for additional measures for waterproof.
Meanwhile, according to the conventional art, to solve the problems, there was presented a water pump motor that is formed by insert-molding a number of split cores with a bulk mould compound (BMC) and inserting a metallic can into the inside thereof.
However, the conventional water pump motor employs an inner rotor structure, and has not only narrow slots between T-shaped teeth provided in a stator core, but also employs an inner coil winding method, to thus cause uneasy coil windings. In addition, the conventional water pump motor needs a separate wiring structure for connection between the coil windings wound in each split core, to thereby cause structure of a motor to become very complex and workability to become significantly deteriorated.
In addition, as described above, the stator is constituted by the inner winding method, and thus a coil winding space is narrow, to thus fail to increase a fill factor and enhance the efficiency of the motor.
Moreover, since an air gap between a rotor and a stator is structurally large in size, an expansive Nd magnet whose magnetic force is stronger than a low-cost ferrite magnet should be used, to thereby cause high production costs. In addition, unless the size of the water pump (in particular, the diameter thereof) is increased, a low-magnetic ferrite magnet may not be used and a high-magnetic Nd magnet should be used, in order to obtain a desired pump output.
However, the Nd magnet has no corrosion resistance unlike a low-cost ferrite magnet having a corrosion resistance capability, and thus should have a water-proof structure surrounding the Nd magnet so that the Nd magnet does not touch the water. As a result, since an air gap between the stator core and the magnet becomes large, the motor efficiency was further degraded.